Raster manipulated television receiver

Abstract

A television receiver is disclosed for selectively displaying either a 525 line NTSC video signal or a 625 line European teletext or Viewdata signal. The receiver includes two vertical countdown circuits: a 525 line countdown circuit for use in generating an NTSC type raster, and a 625 line countdown circuit for use in generating a 625 line raster. Switch means are provided for selecting between the two signals generated by the countdown circuits. The receiver CRT uses self-converging, in-line guns.

What is claimed is: 
     
       1. In a television receiver of the type having means for detecting video signals, means for decoding teletext information, a sync separator, and a vertical deflection circuit and a horizontal deflection circuit providing inputs to a cathode ray tube, the improvement comprising: digital synchronization means for providing vertical synchronization signals in first or second modes, said first mode corresponding to display of signals in a first format, said second mode corresponding to display of signals in a second format, said digital synchronization means being coupled to the sync separator and to the means for decoding teletext information; and   means for selecting one of said first and second modes for use in combination with the vertical deflection circuit, whereby teletext type signals are displayed in said second format.   
     
     
       2. The improvement of claim 1 wherein said digital synchronization means comprises: a first digital synchronization circuit corresponding to said first mode and having an input;   means coupling said first digital synchronization circuit input to the sync separator;   a second digital synchronization circuit corresponding to said second mode and having an input; and   means coupling said second digital synchronization input to the means for decoding teletext information.   
     
     
       3. The improvement of claim 2 wherein said first and second digital synchronization circuits are driven in parallel and wherein said selecting means comprises switch means associated with the vertical deflection circuit for selecting between said first and second digital synchronization circuit. 
     
     
       4. The improvement of claim 1, 2 or 3 wherein said selecting means is responsive to a controller associated with the teletext decoding means. 
     
     
       5. The improvement of claim 1 or 2 wherein the television receiver cathode ray tube includes self-converging, in-line guns. 
     
     
       6. A television receiver for receiving and displaying NTSC video signals in NTSC format or European teletext or Viewdata signals in a format having 24 lines of text comprising: input means including means for demodulating and detecting received video signals;   a sync separator circuit arrangement coupled to receive signals from said input means;   a teletext decoder and control circuitry coupled to said input means;   a CRT;   a horizontal deflection circuit coupled to said CRT and to said sync separator circuit arrangement;   NTSC countdown circuit and a European signal countdown circuit for developing vertical synchronization signals;   means for coupling said NTSC countdown circuit to said sync separator arrangement;   means for coupling said European signal countdown circuit to said teletext decoder and control circuitry;   a vertical deflection circuit having an output coupled to said CRT;   switch means for engaging a selected one of said countdown circuits with said vertical deflection circuit in accordance with the type of signal to be displayed, said switch means being responsively coupled to said teletext circuitry, whereby said CRT is driven at the NTSC rate for displaying an NTSC video picture and is driven at the European rate for displaying European teletext or Viewdata data.   
     
     
       7. The receiver of claim 6 wherein said CRT includes self-converging, in-line guns.